It has hitherto been a general practice for the bearing device to have the model number, precision code, special requirement code and manufacturing lot number marked in the product itself or printed in a package thereof. However, the contents that can be born in the bearing device and/or the package thereof are limited to the minimum.
As IC tags which are affixed to various products and which are compact in size and capable of recording a large amount of information therein, various IC tags for use in radio frequency identification (RFID) have hitherto been developed, which utilizes the RFID technology. (See, for example, the Japanese Laid-open Patent Publication No. 2002-298116.)
However, the bearing identification information represented by the numbering conventionally marked in the packages containing bearing devices has a problem in that it tends to be lost or become illegible after the bearing device has been assembled. The markings made in the respective bearing devices contain so small an amount of information marked, that individual identification of those bearing devices may not be possible to achieve.
In view of the foregoing, attempts have been made to affix an RFID-based IC tag capable of accommodating a large amount of information directly to each of the bearing devices. Where the IC tag is to be fitted to a bearing device, a problem tends to occur, which is associated with absorption and reflection of radio waves in and from raceway members and, therefore, it is considered feasible to fit the IC tag to a sealing member rather than to the raceway member. Specifically, since the RFID-based IC tag makes use of microwaves, mounting of the RFID-based IC tag on the bearing device makes it impossible for the RFID-based IC tag to be read out because during the information reading raceway members and so forth of the bearing device absorb the microwaves. Although the IC tag itself is available, which is so designed as to be affixed directly to metallic components, such tag is expensive and bulky.
However, even where the IC tag is fitted to the sealing member, the RFID-based IC tag having a heat resistance enough to withstand the environment of use of the bearing device must be provided with a member such as, for example, a sheath outside the IC tag. On the other hand, if the antenna of the tag is in the form of a coil antenna, such antenna employs such a structure, in which a winding is spirally wound a number of turns in order to secure a longer distance of travel of radio waves, and the tag including such antenna therefore tends to have an increased size in respective directions widthwise and thicknesswise thereof. In the case of the RFID-based IC tag for general use, an RFID-based IC tag of a size comparable with, for example, a single rice of rice has been developed at the sacrifice of the storage capacity, but the RFID-based IC tag particularly utilizable with the bearing device has no other way than to have a large size to a certain extent in order to secure the heat resistance and the longer distance of travel of radio waves. With increase in size of the IC tag, the IC tag is required be solildly fixed to the sealing member.